Coating treatment method

ABSTRACT

The present invention supplies a solvent to the front surface of a substrate while rotating the substrate. Subsequently, the substrate is acceleratingly rotated to a first number of rotations, and a resist solution is supplied to a central portion of the substrate during the accelerating rotation and the rotation at the first number of rotations. Thereafter, the substrate is deceleratingly rotated to a second number of rotations, and after the number of rotations of the substrate reaches the second number of rotations, the resist solution is discharged to the substrate. The substrate is then acceleratingly rotated to a third number of rotations higher than the second number of rotations so that the substrate is rotated at the third number of rotations. According to the present invention, in application of the resist solution by spin coating, the consumption of the resist solution can be suppressed, and a high in-plane uniformity can be obtained for the film thickness of the resist film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coating treatment method for asubstrate, such as a semiconductor wafer and the like.

2. Description of the Related Art

In the photolithography process in manufacture of a semiconductordevice, a resist coating treatment of applying a resist solution, forexample, onto a semiconductor wafer (hereinafter, referred to as a“wafer”) to form a resist film is performed. As the coating treatmentmethod, the spin coating method is generally employed. The spin coatingmethod is a method of supplying a resist solution R from a nozzle 11 tothe central portion of the front surface of the wafer W with the wafer Wsucked to a spin chuck 10 as shown in FIG. 12, and rotating the spinchuck 10 at a high speed so as to spread the resist solution R outwardin the radial direction of the wafer W by the centrifugal force.

To perform such a resist coating, it is necessary to apply the resistsolution onto the wafer with high in-plane uniformity.

Incidentally, since miniaturization of the pattern of the semiconductordevice and reduction in film thickness are required, various resistsolutions adaptable to such photolithography are developed. However, thecost of the resist solutions is rising more than before because theresist solutions are required to have precise physical properties, sothat the resist solutions are very expensive in the presentcircumstances. Therefore, the consumption of the resist solution needsto be further reduced, and accordingly a coating method is desired whichcan save the resist more than before and ensure a high in-planeuniformity for the film thickness.

Hence, according to a conventionally proposed resist coating method, thesolvent for the resist solution is used to pre-wet the top of the wafer,and the resist solution is supplied to the wafer while the wafer isrotated at a first number of rotations, so that the resist solution isapplied spreading outward in a direction of the radial of the wafer.Immediately after stop of the supply of the resist solution, the waferis decelerated to a second number of rotations to adjust the filmthickness, and then accelerate to a third number of rotations to shakeoff the remaining solution (Japanese Patent Application Laid-open No.H11-260717). In this case, specifically, the first number of rotationsis 4500 rpm, the second number of rotations is 500 rpm, and the thirdnumber of rotations is 3000 rpm.

However, when the supply amount of the resist solution is small, theresist solution has sometimes not fully spread to the edge of the waferwhile the wafer is rotated at the first number of rotations because of aweak centrifugal force exerted on the resist solution. In this case, theresist solution has been further spread while the wafer is rotated atthe third number of rotations so that the resist solution is appliedover the entire wafer. In the case where the resist solution is spreadseparately at two stages as described above, the resist solution driesto decrease in flowability during the rotation of the wafer at thesecond number of rotations and therefore is different in speed ofspreading on the wafer between the case when the wafer is rotated at thefirst number of rotations and the case when the wafer is rotated at thethird number of rotations. More specifically, in the case of the waferwith a diameter of 300 mm, the film thickness of the resist film may bedifferent between the outside and the inside with a circle with a radiusof 120 mm as a boundary (occurrence of a so-called polarization of thefilm thickness), resulting in reduced in-plane uniformity of the filmthickness.

SUMMARY OF THE INVENTION

The present invention has been developed in consideration of the abovepoints and its object is to suppress the consumption of a resistsolution and provide high in-plane uniformity for the film thickness ofthe resist film in application of the resist solution by spin coating.

To attain the above object, according to the present invention, a methodof supplying a solvent for a resist solution to a substrate to wet afront surface of the substrate with the solvent and then coating thesubstrate with the resist solution includes: a first step ofacceleratingly rotating the substrate to a first number of rotationsafter supplying the solvent thereto, and supplying the resist solutionto a central portion of the substrate during at least the acceleratingrotation or the rotation at the first number of rotations (rotationspeed); a second step of thereafter deceleratingly rotating thesubstrate to a second number of rotations, and supplying the resistsolution to the substrate during at least the decelerating rotation orthe rotation at the second number of rotations (rotation speed); and athird step of thereafter acceleratingly rotating the substrate to athird number of rotations (rotation speed) higher than the second numberof rotations, and rotating the substrate at the third number ofrotations.

According to the present invention, the substrate is deceleratinglyrotated to a second number of rotations and rotated at the second numberof rotations during the second step, whereby the dry of the resistsolution on the substrate is suppressed. In addition, the supply of theresist solution to the substrate during the second step improves theflowability of the resist solution on the substrate. Accordingly, whenthe supply amount of the resist solution is small, the resist solutionsmoothly spreads out to the edge of the substrate during the third stepeven if the resist solution does not completely spread to the edge ofthe substrate. This eliminates polarization of the distribution of theresist film to be formed on the wafer W, unlike the prior art, therebyincreasing the in-plane uniformity of the film thickness of the resistfilm. In other words, the coating treatment with high in-planeuniformity of the film thickness can be performed even with a smallamount of resist solution.

The supply of the resist solution in the second step may be performedafter the number of rotations of the substrate reaches the second numberof rotations. In the second step, the resist solution dries fasterduring the time when the substrate is deceleratingly rotated from thefirst number of rotations to the second number of rotations than duringthe time when the substrate is rotated at the second number ofrotations. The supply of the resist solution in the second step isperformed after the number of rotations of the substrate reaches thesecond number of rotations, thus eliminating the resist solution fromdrying during the decelerating rotation. Thus, the flowability of theresist solution can increase to spread more smoothly to the edge of thesubstrate in the third step.

The resist solution supplied in the second step may be supplied from anozzle different from a nozzle for supplying the resist solution used inthe first step. For example, when the resist solution supplied in thesecond step is different from the resist solution supplied in the firststep, the resist solution can be smoothly supplied over the substrate inthe second step by newly providing a nozzle different from the nozzlefor supplying the resist solution used in the first step.

The resist solution supplied in the second step may be supplied to aposition displaced from the central portion of the substrate. Since theresist solution is supplied to a position closer to the edge of thesubstrate, thus allowing the resist solution to smoothly spread to theedge of the substrate in the third step.

The supply of the resist solution in the second step may be performedcontinuously from the supply of the resist solution in the first step.Specifically, the resist solution supplied in the first step may becontinuously supplied also in the second step.

The resist solution supplied in the second step may be a resist solutionlower in viscosity than the resist solution supplied in the first step.The resist solution is decreased in viscosity by changing the ratio ofthe solvent contained in the resist solution. Accordingly, theflowability of the resist solution increases in the third step.

The solvent for the resist solution may be supplied in place of theresist solution supplied in the second step. The solvent is much lowerin viscosity than the resist solution supplied in the first step.Accordingly, the flowability of the resist solution further increases inthe third step.

According to the present invention, the resist solution supplied to thesubstrate improves in flowability and smoothly spreads over thesubstrate, so that that even if the supply amount of the resist solutionis small, the in-plane uniformity of the film thickness of the resistfilm formed on the substrate can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a resist coatingapparatus according to an embodiment;

FIG. 2 is a schematic plan view showing the resist coating apparatusaccording to the embodiment;

FIG. 3 is an explanatory view showing one example of the recipe in whicha profile of the number of rotations of a wafer and the timing of supplyof a resist solution are correlated with each other in the embodiment;

FIG. 4 is an operation explanatory view schematically showing the statesat respective timings of the recipe shown in FIG. 3;

FIG. 5 is a schematic cross-sectional view showing a resist coatingapparatus according to another embodiment;

FIG. 6 is a schematic plan view showing the resist coating apparatusaccording to the other embodiment;

FIG. 7 is an explanatory view showing one example of the recipe in whicha profile of the number of rotations of the wafer and the timing ofsupply of the resist solution are correlated with each other in theother embodiment;

FIG. 8 is an explanatory view showing one example of the recipe in whicha profile of the number of rotations of the wafer and the timing ofsupply of the resist solution are correlated with each other in theother embodiment;

FIG. 9 is a plan view showing a coating and developing system in whichthe resist coating apparatus of the embodiment is incorporated;

FIG. 10 is a schematic configuration view showing the coating anddeveloping system in which the resist coating apparatus of theembodiment is incorporated;

FIG. 11 is an explanatory view showing one example of the recipe inwhich a profile of the number of rotations of the wafer and the timingof supply of the resist solution are correlated with each other in aconventional embodiment; and

FIG. 12 is an explanatory view showing an appearance of the droppedresist solution spreading on the front surface of the wafer in theconventional example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A resist coating apparatus according to an embodiment of the presentinvention will be described with reference to FIG. 1 and FIG. 2.

Numeral 20 in FIG. 1 denotes a spin chuck, which forms a substrateholding unit, is configured to horizontally hold a wafer W by vacuumsuction. The spin chuck 20 can rotate around the vertical by means of arotation drive unit 21 including a motor and so on and can rise andlower. A guide ring 22 having a cross section in an angle shape isprovided below the spin chuck 20, and the outer periphery of the guidering 22 extends bending downward. A cup body 23 is provided in a mannerto surround the spin chuck 20 and the guide ring 22.

The cup body 23 is formed at its upper surface with an opening largerthan the wafer W so that the spin chuck 20 can rise and lower throughit, and formed with a gap 24 forming a drainage path between its sideperipheral surface and the outer periphery of the guide ring 22. Thelower portion of the cup body 23 forms a bending path in conjunctionwith the outer peripheral portion of the guide ring 22 to constitute agas/liquid separating section. An exhaust port 25 is formed at an innerside area of the bottom portion of the cup body 23, and an exhaust pipe25 a is connected to the exhaust port 25. Further, a drain port 26 isformed at an outer side area of the bottom portion of the cup body 23,and a drain pipe 26 a is connected to the drain port 26.

The resist coating apparatus also includes a resist solution nozzle 30for supplying a resist solution R onto the central portion of the frontsurface of the wafer W and a solvent nozzle 40 for supplying a solventS, for example thinner to the central portion of the front surface ofthe wafer W. The resist solution nozzle 30 is connected to a resistsolution supply source 32 for supplying the resist solution R via aresist solution supply pipe 31.

Along the resist solution supply pipe 31, a supply equipment group 33 isalso provided including a valve, a flow control unit and so on. Thesolvent nozzle 40 is connected to a solvent supply source 42 forsupplying the solvent S, for example, thinner via a solvent supply pipe41.

Along the solvent supply pipe 41, a supply equipment group 43 is alsoprovided including a valve, a flow control unit and so on. In thisembodiment, the resist solution supply source 32 and the supplyequipment group 33 correspond to a resist solution supply unit, and thesolvent supply source 42 and the supply equipment group 43 correspond toa solvent supply unit.

The resist solution nozzle 30 is connected, as shown in FIG. 2, to amoving mechanism 35 via an arm 34 bent in an L-shape. The arm 34 isconfigured to be able to move along a guide rail 36 provided along thelength direction (Y-direction) of a treatment container 50 by means ofthe moving mechanism 35 from a waiting region 37 provided outside on oneend side (right side in FIG. 2) of the cup body 23 to the other end sideand move in the vertical direction.

The solvent nozzle 40 is connected, as shown in FIG. 2, to a movingmechanism 45 via an arm 44 bent in an L-shape. The arm 44 can move alongthe guide rail 36 by means of the moving mechanism 45 from a waitingregion 47 provided outside on the other end side (left side in FIG. 2)of the cup body 23 to the one end side and move in the verticaldirection. A carry-in/out port 51 for the wafer W is formed in a sidesurface of the treatment container 50 facing a carry-in region of acarrier arm being a carrier means, and an opening/closing shutter 52 isprovided at the carry-in/out port 51.

The resist coating apparatus includes, as shown in FIG. 1, a controller6 having a computer program for controlling a later-described series ofoperations, and the controller 6 is configured to control the rotationdrive unit 21, the supply equipment groups 33 and 43, and so on. Thecomputer program is stored in a storage medium, for example, a flexibledisk (FD), a memory card, a compact disk (CD), a magneto-optical disk(MO), a hard disk, or the like and installed in a computer being thecontroller 6.

Next, the operation of the above-described embodiment will be described.FIG. 3 shows a profile (recipe) of the number of rotations of the waferW according to the coating method of this embodiment of the presentinvention, and FIG. 4 schematically illustrates the states of a solutionfilm on the front surface of the wafer at respective timings shown inFIG. 3. Note that the time lengths of respective processes in FIG. 3 donot always correspond to the actual time lengths for easy understandingof the technology.

First of all, an external carry arm holding the wafer W (for example, acarrier arm A2 or A3 in FIG. 10) outside the resist coating apparatusenters the container 50 via the carry-in/out port 51 (see FIG. 2) andtransfers a 12-inch size wafer W to the spin chuck 20 therefrom. Thistransfer may be performed by raising the spin chuck 20 or by usingnot-shown raising and lowering pins. The wafer W is then held on thespin chuck 20 by suction, and the solvent nozzle 40 moves to a positionabove the central portion of the wafer W and supplies, for example, 2.0ml of the solvent S, for example, thinner onto the central portion ofthe standing-still wafer W therefrom.

Subsequently, the solvent nozzle 40 is moved from the position above thecentral portion of the wafer W, and instead, the resist solution nozzle30 is moved to a position above the central portion of the wafer W, andthe wafer W is rotated by controlling the rotation drive unit 21 so thatthe number of rotations of the wafer W is increased to 1000 rpm at anacceleration of 10000 rpm/sec. At the point in time when the number ofrotations reaches 1000 rpm, the resist solution nozzle 30 starts todischarge the resist solution R onto the central portion of the wafer W,and the number of rotations is increased to 2200 rpm that is a firstnumber of rotations. The step in which the number of rotations of thewafer W is increased from 1000 rpm to reach the first number ofrotations shall be a first step here.

The states on the front surface of the wafer W so far are shown at (i),(ii), and (iii) in FIG. 4. The time required for the number of rotationsof the wafer W to reach 1000 rpm is 0.1 seconds, and the wafer is thusrotated at 1000 rpm in a moment, so that the solvent S supplied on thecentral portion of the wafer W is spread outward, that is, pre-wettingis performed, whereby the front surface of the wafer W becomes wet withthe solvent S ((i) in FIG. 4).

Then, from the point in time when the number of rotations reaches 1000rpm, the resist solution R is dropped onto the central portion of thewafer W, so that the resist solution R is smoothly diffused without anytrouble to cause no unevenness in coating due to spreading in streaks,and the number of rotations of the wafer W is further increased, whilethe resist solution R continues to be dropped onto the central portionof the wafer W during the increase (during acceleration) ((ii) in FIG.4).

The time for the number of rotations of the wafer W to increase from1000 rpm to reach 2200 rpm and be subsequently maintained at 2200 rpmfor rotation is 1.6 seconds, while the resist solution nozzle 30discharges 0.4 ml of the resist solution R in 1.6 seconds. However,since the amount of resist solution R discharged is small in the firststep, the resist solution R may not have spread over the entire frontsurface of the wafer W when the number of rotations of the wafer Wreaches 2200 rpm ((iii) in FIG. 4).

Rotation of the wafer W at high speed of the first number of rotationswill dry the resist solution R. Hence, after the number of rotations ofthe wafer W reaches 2200 rpm, the control shifts to a deceleration stateinstantaneously to decelerate the rotation to a second number ofrotations at which drying hardly proceeds. It is preferable to performthe deceleration as soon as possible, in which the rotation isdecelerated to the second number of rotations, for example, to 100 rpm,for example, at an acceleration (a negative acceleration) of 30000rpm/sec. The time required to decrease the number of rotations from thefirst number of rotations to the second number of rotations ispreferably, for example, within 0.2 seconds.

Note that the second number of rotations is not limited to 100 rpm, butis preferably 500 rpm or less. Besides, the time for the number ofrotations to decrease from the first number of rotations to the secondnumber of rotations and be subsequently maintained at the second numberof rotations is, for example, 0.6 seconds, and the time may be adjusteddepending on the viscosity or the like of the resist solution R. Thestep in which the number of rotations of the wafer W is decreased fromthe first number of rotations to the second number of rotations and thewafer W is rotated at the second number of rotations shall be a secondstep here.

When the number of rotations of the wafer W reaches the second number ofrotations in the second step, the resist solution nozzle 30 dischargesagain 0.1 ml of the resist solution R in 0.4 seconds as shown at (iv) inFIG. 4. Discharge of the undried resist solution R improves theflowability of the resist solution R on the wafer W.

After the wafer is rotated at the second number of rotations, the numberof rotations of the wafer W is increased, for example, to a third numberof rotations lower than the first number of rotations and maintained atthe third number of rotations for a while, for example, for 20 seconds.The step in which the number of rotations of the wafer W is increasedfrom the second number of rotations to the third number of rotations andthe wafer W is rotated at the third number of rotations shall be a thirdstep here. In the third step, the resist solution R spreads over theentire front surface of the wafer W and the remaining resist solution Ris also shaken off so that the film thickness is adjusted.

The third number of rotations and its duration are determined dependingon the target film thickness, the viscosity of the resist solution R andso on, and the number of rotations for the 12-inch size wafer ispreferably 2000 rpm or less and is set, for example, to 750 rpm to 2000rpm. The wafer W is thereafter subjected to rinse treatment for its rearsurface and then transferred to the external carrier arm by theoperation reverse to that for the above-described carry-in.

According to this embodiment, drying of the resist solution R on thewafer W is restrained by decreasing the rotation of the wafer W down tothe second number of rotations during the second step and rotating thewafer W at the second number of rotations. The discharge of the resistsolution R at the same tie during the second step increases theflowability of the resist solution R.

Accordingly, when the supply amount of the resist solution R is small,the resist solution R smoothly spreads out to the edge of the wafer Wduring the third step even if the resist solution R does not completelyspread to the edge of the wafer W in the first step. This eliminatespolarization of the distribution of the resist film to be formed on thewafer W, unlike the prior art, thereby increasing the in-planeuniformity of the film thickness of the resist film. In other words, thecoating treatment with a high in-plane uniformity of the film thicknesscan be performed even with a small amount of resist solution R.

In the second step, the resist solution R dries faster during the timewhen the wafer W is deceleratingly rotated from the first number ofrotations to the second number of rotations than during the time whenthe wafer W is rotated at the second number of rotations. In thisembodiment, the discharge of the resist solution R in the second step isperformed after the number of rotations of the wafer W reaches thesecond number of rotations, thus eliminating the resist solution R fromdrying during the decelerating rotation. Thus, the flowability of theresist solution R can increase to spread more smoothly to the edge ofthe substrate in the third step.

Further, on inspection by the inventors, the supply amount of the resistsolution in this embodiment can be reduced by about 20% compared to thesupply amount of the resist solution required to obtain the samein-plane uniformity by using the prior method as that by thisembodiment.

It should be noted that the first number of rotations is preferably 4000rpm or less and more preferably 2000 rpm to 4000 rpm for the 12-inchsize wafer W. The first number of rotations is preferably 6000 rpm orless and more preferably 3000 rpm to 5000 rpm for the 8-inch size waferW. Further, the third number of rotations is preferably 4000 rpm or lessfor the 8-inch size wafer W.

In the above-embodiment, in place of the resist solution R dischargedduring the second step, a resist solution R may be used which is lowerin viscosity than the resist solution R discharged during the firststep. The resist solution R discharged during the second step isdecreased in viscosity by changing the ratio of the solvent contained inthe resist solution R. In this case, the resist coating apparatus isfarther provided with a resist solution nozzle 60 for discharging theresist solution R during the second step as shown in FIG. 5. The resistsolution nozzle 60 is connected to a resist solution supply source 62for supplying the resist solution R via a resist solution supply pipe61. Along the resist solution supply pipe 61, a supply equipment group63 is also provided including a valve, a flow control unit and so on.The supply equipment group 63 is connected to the controller 6 thatcontrols the flow rate, the discharge timing, and so on of the resistsolution R discharged from the resist solution nozzle 60.

The resist solution nozzle 60 is connected, as shown in FIG. 6, to amoving mechanism 65 via an arm 64 bent in an L-shape. The arm 64 isconfigured to be able to move in a horizontal direction (Y-direction)along the guide rail 36 by means of the moving mechanism 65 from awaiting region 67 or 68 provided outside the cup body 23 and move in thevertical direction. The waiting region 67 is provided between theoutside of the cup body 23 (right side in FIG. 6) and the waiting region37, and the waiting region 68 is provided between the outside of the cupbody 23 (left side in FIG. 6) and the waiting region 47.

Next, a method of discharging the resist solution R from the resistsolution nozzle 60 will be described. While the resist solution nozzle30 is discharging the resist solution R in the first step, the resistsolution nozzle 60 is waiting in the waiting region 68. After completionof the discharge of the resist solution R from the resist solutionnozzle 30, the resist solution nozzle 30 moves to the waiting region 37.Upon start of the second step, the resist solution nozzle 60 moves to aposition above the central portion of the wafer W, and discharges theresist solution R when the number of rations of the wafer W reaches thesecond number of rotations. After completion of the discharge of theresist solution R from the resist solution nozzle 60, the resistsolution nozzle 60 moves to the waiting region 67 and waits at thewaiting region 67 during the third step.

As described above, the resist solution R discharged in the second stepis low in viscosity than the resist solution R discharged in the firststep, so that the resist solution increases in flowability in the thirdstep to smoothly spread to the edge of the wafer W during the thirdstep. Accordingly, the in-plane uniformity of the film thickness of theresist film increases.

In the above embodiment, in place of the resist solution R dischargedduring the second step, the solvent S may be used. In this case, in thesecond step, the solvent S is discharged from the solvent nozzle 40. Thesolvent S is much lower in viscosity than the resist solution R suppliedin the first step. Accordingly, the flowability of the resist solution Rfurther increases in the third step, so that the in-plane uniformity ofthe film thickness of the resist film further increases.

The resist solution R or the solvent S discharged in the second step maybe discharged to a position displaced from the central portion of thewafer W. More specifically, in the second step, the resist solutionnozzle 30, the resist solution nozzle 60, or the solvent nozzle 40 movesto a position displaced from the position above the center portion ofthe wafer W and discharges the resist solution R or the solvent S. Inthis case, the resist solution R or the solvent S is discharged to aposition closer to the edge of the wafer W, thus allowing the resistsolution R to smoothly spread to the edge of the substrate in the thirdstep.

Further, the discharged of the resist solution R in the second step maybe performed continuously from the discharge of the resist solution R inthe first step. In other words, as shown in FIG. 7, the resist solutionR discharged from the resist solution nozzle 30 in the first step iscontinuously discharged while the number of rotations of the wafer W isdecreased from the first number of rotations to the second number ofrotations and maintained at the second number of rotations. Morespecifically, when the number of rotations of the wafer W starts to bedecreased from the first number of rotations, an amount of resistsolution R of 0.1 ml is discharged in 0.4 seconds in the second step.The in-plane uniformity of the film thickness of the resist film can bemade higher also in this case than in the case when the resist solutionis applied by the conventional method as clear from a later-describedexample 1.

As for the discharged of the resist solution R in the first step, thedischarge may be started during accelerating rotation of the wafer W tothe first number of rotations and stopped by the time when the number ofrotations reaches the first number of rotations, or the discharged maybe started during the rotation at the first number of rotations.

Further, the number of rotations of the wafer W is not limited to thatafter the number of rotations of the wafer W reaches the first number ofrotations, the first number of rotations is maintained for a while, butmay be decreased to the second number of rotations immediately afterreaching the first number of rotations as shown in FIG. 8.

Next, just for reference, the whole configuration of a coating anddeveloping system in which the above-described resist coating apparatusis incorporated and to which an aligner is connected will be describedwith reference to FIG. 9 and FIG. 10. In FIG. 9 and FIG. 10, symbol B1denotes a carrier station for carry-in/out a carrier 8 hermeticallyhousing a plurality of wafers W, for example, 13 wafers W, and amounting section 80 capable of mounting a plurality of carriers 8arranged side by side thereon, opening/closing units 81 provided in thewall surface on the front side as viewed from the mounting section 80,and a transfer means A1 for taking the wafers W out of the carriers 8via the opening/closing units 81, are provided in the carrier stationB1.

To the rear side of the carrier station B1, a processing block B2 isconnected which is surrounded by a housing 82, and shelf units U1, U2and U3 in each of which units of heating and cooling systems aremulti-tiered and main arms A2 and A3 forming substrate carrier means fortransferring the wafer W between the units in shelf units U1, U2 and U3and solution treatment units U4 and U5 are provided arranged alternatelyin sequence from the front side in the processing block B2. Further,each of the main arms A2 and A3 is placed in a space surrounded by apartition wall 83 composed of face portions on the side of the shelfunits U1, U2, and U3 which are arranged in a forward and backwarddirection as viewed from the carrier station B1, one face portion on theside of, for example, the later-described solution treatment unit U4 orU5 on the right side, a rear face portion forming one face on the leftside. Numerals 84 and 85 in FIG. 9 and FIG. 10 denote temperature andhumidity regulating units each comprising a temperature regulator, aduct for regulating the temperature and humidity and so on for treatmentsolutions used in the units.

The solution treatment units U4 and U5 are configured such that theabove-described resist coating apparatuses (COT) 90 for applying theresist solution to the front surface of the wafer W, developing units(DEV) 87 for applying a developing solution to front surface of thewafer W, antireflection film forming units (BARC) and so on aremulti-tiered, for example, five-tiered on chemical storage unit 86 forthe resist solution R, the developing solution and so on, for example,as shown in FIG. 10. Besides, the already-described shelf units U1, U2,and U3 are configured such that various kinds of units for performingpre-processing and post-processing of the treatments performed in thesolution treatment units U4 and U5 are multi-tiered, for example,ten-tiered, in which the combination of the units includes a heatingunit for heating (baking) the wafer W, a cooling unit for cooling thewafer W, and so on.

To the rear side of the shelf unit U3 in the processing block B2, analigner B4 is connected via an interface section B3 composed of a firstcarrier chamber 88 a and a second carrier chamber 88 b. Inside theinterface section B3, an edge exposure unit (WEE) for selectivelyexposing only an edge portion of the wafer W, a buffer cassette (SBU)for temporarily housing a plurality of, for example, 25 wafers W, atransfer unit (TRS 2) for transferring the wafer W, a high-precisiontemperature regulating unit (CPL), for example, having a cooling plateand so on are provided in addition to two transfer means A4 and A5 fortransferring the wafer W between the processing block B2 and the alignerB4.

Taking an example of the flow of the wafer W in this system, when thecarrier 8 housing wafers W is carried in from the outside and mounted onthe mounting table 80, the lid body of the carrier 8 is removed togetherwith the opening/closing unit 81, and a wafer W is taken out by thetransfer means A1. The wafer W is transferred via a transfer unit (notshown) forming one tier in the shelf unit U1 to the main carrier meansA2 and subjected, for example, to hydrophobic treatment and coolingprocessing as the pre-processing of the coating treatment in one shelfin one of the shelf units U1 to U3. Thereafter, the resist solution isapplied to the front surface of the wafer W in the resist coatingapparatus (COT) 90, and a water-repellent protection film is then formedon the front surface of the wafer W having the resist film formedthereon in a protection film forming unit (TC) 3 being a protection filmforming section.

Subsequently, the wafer W is heated (baking processing) in the heatingunit (PAB) forming one tier in one of the shelf units U1 to U3, thencooled, and carried via the transfer unit (TRS 1) in the shelf unit U3into the interface section B3. In the interface section B3, the wafer Wis carried by the transfer means A4, for example, from the edge exposureunit (WEE), to the buffer cassette (SBU), and then to the high-precisiontemperature regulating unit (CPL), and the wafer W mounted on thehigh-precision temperature regulating unit (CPL) is carried by thetransfer means A5 to the aligner B4 where the wafer W is subjected toexposure processing. The exposed wafer W is carried by the transfermeans A5 to the transfer unit (TRS 2) and then carried by the transfermeans A5 from the transfer unit (TRS 2) to the heating unit (PEB) in theshelf unit U3.

In the developing unit (DEV) forming one tier in the shelf unit U5, thedeveloping solution is supplied to the front surface of the wafer W todevelop the resist, whereby a resist mask in a predetermined pattern isformed on the wafer W. Thereafter, the wafer W is returned by thetransfer means A1 to the original carrier 8 on the mounting table 80.

A preferred embodiment of the present invention has been described abovewith reference to the accompanying drawings, but the present inventionis not limited to the embodiment. It should be understood that variouschanges and modifications within the scope of the spirit as set forth inclaims are readily apparent to those skilled in the art, and thoseshould also be covered by the technical scope of the present invention.

Example

Hereinafter, the effect of the coating treatment method of the presentinvention will be described comparing to that of the conventionalcoating treatment method. As the apparatus for performing both methods,the resist coating apparatus shown in FIG. 1 and FIG. 2 was used.

The recipe shown in FIG. 7 illustrated above was used as the recipe forcoating the resist solution R in the experiment by the coating treatmentmethod of the present invention.

The recipe shown in FIG. 11 was used as the recipe for coating theresist solution R in the experiment performed by the conventionalcoating treatment method. In the recipe shown in FIG. 11, the firstnumber of rotations is 2050 rpm. The time for the number of rotations ofthe wafer W to increase from 1000 rpm to reach 2050 rpm and besubsequently maintained at 2050 rpm for rotation is 1.5 seconds, while0.5 ml of the resist solution is discharged in 1.5 seconds.

Subsequently, the rotation is decelerated from the first number ofrotations to 100 rpm that is the second number of rotations andmaintained at the second number of rotations, the time required forwhich is 1 second, during which the resist solution is never discharged.The remaining recipe is the same as that of the recipe shown in FIG. 7.

Note that in performing both experiments, the supply amounts of theresist solution R to the wafer W in both cases are 0.5 ml to form aresist film with a film thickness of 250 nm on the wafer W. Bothexperiments were performed using the above recipes on 13 wafers W,respectively.

The experiments were performed as describe above, and the distributionsof the film thickness of the resist films formed on the wafers W wereexpressed by the three sigma method to evaluate the variations in thedistributions. In the case of experiment performed using theconventional method, the distribution of the film thickness of theresist film indicated a three sigma (3σ) of 1.8 nm to 2.0 nm.

On the other hand, in the case of experiment performed using the coatingtreatment method of the present invention, the distribution of the filmthickness of the resist film indicated a three sigma (3σ) of 0.6 nm to0.7 nm. In other words, it was found that the variation in thedistribution of the film thickness is smaller in the coating treatmentmethod of the present invention than in the conventional method.Accordingly, it was found that the resist solution R can be applied tothe wafer W with higher in-plane uniformity in the coating treatmentmethod of the present invention than in the conventional method.

The present invention is in useful when applying a coating solution suchas the resist solution or the like to a substrate such as asemiconductor wafer or the like.

1. A method of supplying a solvent for a resist solution to a substrateto wet a front surface of the substrate with the solvent and thencoating the substrate with the resist solution, said method comprising:a first step of acceleratingly rotating the substrate to a first numberof rotations after supplying the solvent thereto, and supplying theresist solution to a central portion of the substrate during at leastthe accelerating rotation or the rotation at the first number ofrotations; a second step of thereafter deceleratingly rotating thesubstrate to a second number of rotations, and supplying the resistsolution to the substrate during at least the decelerating rotation orthe rotation at the second number of rotations; and a third step ofthereafter acceleratingly rotating the substrate to a third number ofrotations higher than the second number of rotations, and rotating thesubstrate at the third number of rotations, wherein the resist solutionsupplied in said second step is a resist solution lower in viscositythan the resist solution supplied in said first step.
 2. The coatingtreatment method as set forth in claim 1, wherein the supply of theresist solution in said second step is performed after the number ofrotations of the substrate reaches the second number of rotations. 3.The coating treatment method as set forth in claim 1, wherein the resistsolution supplied in said second step is supplied from a nozzledifferent from a nozzle for supplying the resist solution used in saidfirst step.
 4. The coating treatment method as set forth in claim 1,wherein the resist solution supplied in said second step is supplied toa position displaced from the central portion of the substrate.
 5. Thecoating treatment method as set forth in claim 1, wherein the supply ofthe resist solution in said second step is performed continuously fromthe supply of the resist solution in said first step.